Electric engine coolant heater

ABSTRACT

A heater for warming coolant in a liquid-cooled engine, including a reservoir for coolant, the reservoir having an inlet and an outlet, a one-way inlet valve to permit coolant to enter the reservoir, a one-way outlet valve to permit coolant to leave the reservoir, a heating element in the reservoir, and a thermostat for controlling the heating element. The thermostat cuts out when the temperature of the coolant in the reservoir is above the boiling point of the coolant, so that the coolant is vaporized. After the heating element is turned off, the remaining vapor in the reservoir condenses, and the resulting partial vacuum draws in a fresh charge of coolant through the inlet, some of which proceeds immediately through the outlet to ram the heated coolant through the cooling system. The heating element is again energized and the cycle is repeated.

United States Patent [72] Inventors Walter J. Woytowleh Deep River,Ontario; Charles G. Shepherd, Oakville, Ontario, both of Canada [21]Appl. No. 827,767

[22] Filed May 26, 1969 [45] Patented Dec. 7, 1971 [73] Assignee BardonResearch and Development Limited Toronto, Canada a part interest [541ELECTRIC ENGINE COOLANT HEATER 56] References Cited UNITED STATESPATENTS 1,492,153 4/1924 Van Hise et a1 103/255 2,440,610 4/ 1948Kimberlin 219/208 2,505,286 4/1950 Gratsinger 123/1425 X PrimaryExaminer-A. Bartis Attorney-Rogers, Bereskin & Parr ABSTRACT: A heaterfor warming coolant in a liquid-cooled engine, including a reservoir forcoolant, the reservoir having an inlet and an outlet, a one-way inletvalve to permit coolant to enter the reservoir, a one-way outlet valveto permit coolant to leave the reservoir, a heating element in thereservoir, and a thermostat for controlling the heating element. Thethermostat cuts out when the temperature of the coolant in the reservoiris above the boiling point of the coolant, so that the coolant isvaporized. After the heating element is turned off, the remaining vaporin the reservoir condenses, and the resulting partial vacuum draws in afresh charge of coolant through the inlet, some of which proceedsimmediately through the outlet to ram the heated coolant through thecooling system. The heating element is again energized and the cycle isrepeated.

ELECTRIC ENGINE COOLANT HEATER This invention relates to a heater forprewarming the coolant of a liquid-coolant engine during cold weatherwhen the engine is at rest.

Reliable starting of internal combustion engines (particularlyautomobile engines) in cold weather often requires the use of anauxiliary heater for warming the engine coolant. Such heaters employelectrical heating elements and they are energized by connecting them tothe usual electrical mains. The heat provided by the auxiliary heaterhelps to lower the viscosity of the engine lubricant and to improve thevaporization of the fuel so that the engine is easier to crank and thefuel is easier to ignite. There are two types of such heaters which arein fairly general use: l) the block heater, and (2) the tank heater. Theblock heater is designed to be inserted directly into the cooling systemof the engine, for example through a frost plug. Although this type ofheater is reasonably efficient, installation frequently posesdifficulties even for mechanics having proper tools. Also, the blockheater normally operates continuously, and frequently more power isconsumed than actually is needed. The installation of tank heaters isrelatively time consuming, particularly for the average car owner, andconventional tank heaters rely mainly on convection to heat the engineblock. The resulting circulation of coolant does not always uniformlywarm the engine.

The heater of the present invention is of the tank type. It is simple toinstall (the cooling system need not be drailed in most cases) and itprovides a relatively strong flow of coolant to adequately heat theengine block. Furthermore, the supply of electricity to the heater isregulated so that only enough power is consumed to keep the enginecoolant at a predetermined temperature.

A preferred form of the invention includes a reservoir having an inletand an outlet, a one-way inlet valve to permit coolant to enter thereservoir, a one-way outlet valve to permit coolant to be expelled fromthe reservoir, a heating element in the reservoir and a thermostatelectrically connected to the heating element. The thermostat has upperand lower temperature limits; at the upper limit the heating element isturned off, and at the lower limit the heating element is turned on. Theupper limit is selected so that the coolant in the reservoir isvaporized. whereupon it is expelled forcibly through the outlet. Theheating element turns off after much of the coolant in the reservoir hasvaporized, and the remaining vapor in the reservoir condenses, creatinga partial vacuum which draws in a fresh charge of coolant into thereservoir. The fresh charge enters the reservoir with considerableforce, and a substantial portion of it passes through the outlet andtends to ram the heated coolant through the cooling system. Whensufficient incoming coolant has entered the reservoir so that thetemperature sensed by the thermostat has dropped to the lower limit, theheating element is again turned on and the cycle is repeated. Anadvantage of the present invention is that the reservoir can beconnected in the cooling system of an automobile engine by simplycutting an existing hose leading from the interior heater and connectingthe cut ends of the hose to the inlet and outlet of the reservoir. Thetime required for installation is comparatively short, and only simpletools are needed.

In the drawings which illustrate a preferred embodiment of theinvention:

FlG. l is a perspective view, partly broken away, showing a heater;

FIG. 2 is a sectional view of a one-way outlet valve used in the heaterof FIG. 1; and

FIG. 3 is an exploded view of an inlet valve used with the heater of HG.1.

Referring to FIG. 1, a tank heater 10 is designed to be installed in thecooling system of a liquid-cooled internal combustion engine,particularly an automobile having an interior heater of the heatexchanger type. The interior heater is usually connected to the coolingsystem by a hose leading from the water pump of the engine. The heater10 is conveniently installed by cutting said hose as near to the waterpump as practicable and connecting the ends of the cut hose to theheater 10. as will be explained in more detail below.

The heater 10 includes a two-piece housing 12, a one-way inlet valve 14,a one-way outlet valve 16, a heating element 18, and a thermostat 20.

The housing 12 is of noncorrosive material, such as zinc or aluminum andit comprises a cylindrical shell 22 having an end wall 24 in which anoutlet opening is formed, and an end member 26 which can be secured tothe shell 22 by any conventional means (not shown) to provide aliquidtight seal. The shell 22 and the end member 26 when joinedtogether form a reservoir into which coolant is drawn, heated until itvapourizes and then expelled, as discussed below. The end wall 24 of theshell 22 is formed with a generally cylindrical, tubular, open-endedboss 28 which extends both inwardly and outwardly of the end wall 24.The boss 28 constitutes an outlet for the tank 10. The outer end of theboss 28 is internally threaded to receive an adapter 30 foraccommodating hoses which will not fit onto the boss 28 directly. Theboss 28 and the adapter 30 are respectively provided with grooves 32, 34in their outer surfaces to facilitate the attachment of a hose with aconventional hose clip. The inner end of the boss 28 is shaped toreceive the valve 12, as shown in FIG. 2, and explained more fullybelow.

The end member 26 of the housing 12 has an outwardly projecting,cylindrical, tubular, open-ended boss 36 the axis of which is preferablyin line with the axis of the boss 28. The boss 36 constitutes an inletfor the tank 10. The outer end of the boss 36 is provided with internalthreads for receiving an adapter 38 that is similar to the adapter 34,and likewise grooves 40, 42 are respectively provided in the outersurfaces of the boss 36 and the adapter 38 to facilitate attachment of ahose by means of conventional hose clamps. The inner end of the boss 36is formed to receive the valve 14, as shown in F IG. 3 and explainedmore fully below.

The end member 26 includes an outwardly projecting generallysemicylindrical portion 44 that is integral with an end wall 46. Theportion 44 of the end member 26 opens outwardly, but it is closed by aremovable cover plate 48 which can be held in place by screws or otherconventional means. The cover plate 48 has a central opening throughwhich an electrical cable (not shown) can be inserted. The inlet valve14 includes a generally circular disc 50 the center of which is slightlydished, and which is preferably of aluminum or cadmium plated steel. Thedisc 50 is formed with two opposed, outwardly projecting tabs 52 (HO.3), and the inner end of the boss 36 is formed with recesses 54 forreceiving the tabs 52 so that the disc 50 can hang downwardly with thetabs 52 in the recesses 54. The inner end of the boss 36 is furtherformed with a circular recess 56 that is slightly larger in diameterthan the diameter of the disc 50, and the recess 56 terminates at itsinner end in a shoulder 58 against which the disc 50 is seated when itis in its closed position. The disc 50 is held in place by a washer 60(also preferably of aluminum or cadmium plated steel) that isfrictionally engaged in a circular recess 62 formed in the outer end ofthe boss 36, and the internal diameter of the washer 60 is larger thanthe diameter of the disc 50 so that the disc 50 can freely swingupwardly through the washer 60 to an open position, where there isrelatively little restriction to the flow of incoming coolant. The disc50 fits rather loosely in place, but when the pressure in the reservoirbuilds up the disc 50 is pressed firmly against the shoulder 58 tothereby prevent any vapor from being expelled through the inlet of theheater 10.

The outlet valve 16 is very similar to the inlet valve 14, except thatit is arranged so that the fluid is permitted to flow only out of theheater l0 and not into it. The valve 14 includes a disc 64 that isidentical to the disc 50, and it hangs inside a recess formed in theboss 28 in a manner similar to the disc 50. ln its open position, asshown in FIG. 2, the disc 64 can swing upwardly in the same direction asthe disc 50. The disc 64 is held in place by a washer 66, but in thiscase the washer 66 has an internal diameter that is smaller than thediameter of the disc 64 so that the washer 66 constitutes a valve seatfor the disc 64. In its closed position, as shown in solid lines in FIG. 2, the disc 64 is pressed against the outer surface of the washer66.

The heating element 18 is conventional, and it may be in the from of aloop of one or more turns, which preferably is positioned near thebottom of the housing 12. The heating element 18 is provided with ends68, 70 that are engaged in openings formed in the end member 26 of thehousing 12, and the ends 68, 70 can be retained in place by swagging thesurrounding metal of the end member 26 to provide a firm and leak proofseal. Electrical terminals 72, 74 respectively protrude from the ends68, 70 of the heating element 18, and they are of course electricallyinsulated from the housing 12. The heating element 18 can be designed tooperate at the usual main voltages (eg 1 l or 220 volts AC).

The thermostat 20 is rigidly attached to the end wall 46 of the endmember 26, between the ends 68, 70 of the heating element. The innersurface of the end wall 46 directly opposite the thermostat 20 is formedwith a recess 75 which receives a portion of the heating element 18, sothat there is reasonably good thermal contact between the outer surfaceof the heating element 18 and the thermostat 20. The thermostat 20 hastwo terminals 76, 78 and is connected in series with the heating element18 by a lead (not shown) so that the heating element is controlled bythe thermostat 20. The thermostat 20 has an upper limit at which thethermostat turns off the heating element 18 and a lower limit at whichthe heating element is turned on. The upper limit is such that coolantin the reservoir is vaporized before the heating element 18 is turnedoff; the lower limit determines the average temperature of the coolantin the cooling system. In a prototype of the heater 10, an upper limitof 250 F. and a lower limit of l70 F. was used; these limits were foundto be satisfactory in a six cylinder engine with a 50 percent glycolantifreeze mixture, which was kept at an average temperature of 70 F.

The heater is most conveniently installed in a horizontal position, asthis position usually involves little or no .sharp bends in theconnecting hoses. in addition, the heater 10 should be installed atabout the upper level of the coolant in the engine block. if the heater10 is installed too low, the coo lant tends to circulate continuously byconvection and the desired vapourization does not'take place to the sameextent. It is conceivable that the heater 10 could be installedvertically, with the inlet at the top, but this is not as desirable asthe horizontal position in most automobile installations because theheater hose to which connection is made is most frequently horizontallydisposed in most cases the installation of the heater l0 simply entailscutting the hose leading from the water pump to the interior heater andattaching the cut ends of the hose to the respective bosses 28 and 36,with the hose leading from the water pump connected to the outlet of theheater 10. The hose should be raised to at least the level of the top ofthe radiator to avoid loss of coolant. Hose clamps can then be installedto secure the hoses on the bosses 28 and 36. The engine should then beidled for several minutes to fill the heater 10 with coolant.Alternatively, the heater 10 could be filled with antifreeze beforeinstallation.

In operation, the heater 10 is connected with a suitable source ofelectrical power. When the temperature of the coolant n the reservoir ofthe housing 12 falls below the low limit of the thermostat 20, theheating element 18 is energized and it remains energized until most ofthe coolant in the reservoir is vaporized. The hot vapor is expelledthrough the outlet valve 16, and eventually condenses and mixes with thecoolant downstream from the heater 10. When the high temperature limitof the thermostat 20 has been reached, the heating element isdisconnected from the power source and remains disconnected until thetemperature has again dropped to the low temperature limit. Theremaining vapor in the reservoir condenses and the resulting partialvacuum draws in a fresh charge of coolant through the inlet valve 14.The fresh charge of coolant enters the reservoir with considerableforce, and a considerable portion of it continues directly through thereservoir and the outlet valve. As explained above this action tends toram the heated coolant through the cooling system. When the temperaturedrops to the low limit of the thermostat 20, the heating element againis energized and the cycle is repeated. It will thus be noted that theoperation of the heating element 18 is not continuous, but instead isperiodic. The average amount of power consumed depends on the ambienttemperature, wind, etc., for example it was determined in a prototypeheater that power consumption varies from about 850 watts at 20 F. towatts at +32 F., to maintain an engine temperature of about 50 F.

In a prototype of the heater, the separation between the valves wasabout 2 three-quarter inches, the diameter of the discs 50 and 64 wasabout one-half inch. The heating element 18 was rated at 850 watts.

What we claim as our invention is:

1. A heater for warming liquid coolant in a cooling system of an engineand for forcing said coolant through the cooling system without creatingany appreciable convection current in said heater, said heatercomprising:

a. an enclosed reservoir for containing liquid coolant, said reservoirhaving a fluid inlet and a fluid outlet to permit said reservoir to beconnected in said cooling system with said coolant substantially fillingsaid reservoir;

b. a one-way inlet valve in communication with said fluid inlet topermit coolant to flow into said reservoir and to prevent coolant fromleaving said reservoir through said fluid inlet;

c. a one-way outlet valve in communication with said fluid outlet topermit heated coolant to leave said reservoir and to prevent coolantfrom entering said reservoir through said fluid outlet; 7

d. an electrical heating element coupled to said reservoir for heatingsaid coolant; and

e. a thermostat having an upper limit and a lower limit, said thermostatbeing electrically connected to said heating element to control thesupply of electricity to said heating element, said thermostat beingpositioned so that it is in thermal contact with the contents of saidreservoir and is responsive to the temperature of said coolant in saidreservoir in both its liquid and vapor states, the supply of electricityto said heating element being interrupted when the temperature sensed bythe thermostat reaches said upper limit, and being resumed when saidtemperature falls to said lower limit, said upper limit being such thatat least a portion of the liquid coolant in said reservoir is vaporizedwhen said heating element is energized and heated coolant is expelledthrough said outlet, the heating element being disconnected from itssupply of electricity by said thermostat when said upper limit has beenreached, whereupon the temperature in said reservoir falls so that thevapor pressure in said reservoir drops substantially thereby drawing afresh charge of liquid coolant into said reservoir through said fluidinlet.

2. A heater as claimed in claim 1 wherein said fluid inlet and saidfluid outlet are substantially in alignment and said heating element isin said reservoir.

3. A heater as claimed in claim 2 wherein said inlet valve comprises afirst disclike member positioned at the inner end of said fluid inletagainst an end wall of said reservoir, said first disclike member beingpivotally mounted and the inner end of said fluid inlet being shaped toprovide a seat for said first dis clike member when said first disclikemember is pressed against said fluid inlet inner end.

4. A heater as claimed in claim 3 wherein said outlet valve comprises asecond disclike member positioned at the inner end of said fluid outletagainst an opposite end wall of said reservoir, said second disclikemember being pivotally mounted, and a washer secured to said oppositeend wall and positioned inwardly of said second disclike member toprovide a seat for the same.

5. A heater as claimed in claim 2 wherein a portion of said heatingelement is adjacent to an inner surface of a wall of said reservoir. andsaid thermostat is in contact with an outer surface of said wallopposite said portion of said heating element, said wall being thermallyconductive.

6. in combination with an engine cooling system containing liquidcoolant, a heater for warming the liquid coolant and for forcing saidcoolant through the cooling system. the heater being positioned at aboutthe upper level of coolant in the system so that the heater issubstantially full of coolant; the heater comprising an enclosedreservoir for containing liquid coolant, said reservoir having a fluidinlet and a fluid outlet to permit said reservoir to be connected insaid cooling system with said coolant substantially filling saidreservoir; a one-way inlet valve in communication with said fluid inletto permit coolant to flow into said reservoir and to prevent coolantfrom leaving said reservoir through said fluid inlet; a one-way outletvalve in communication with said fluid outlet to permit heated coolantto leave said reservoir and to prevent coolant from entering saidreservoir through said fluid outlet; an electrical heating elementcoupled to said reservoir for heating said coolant; and a thermostathaving an upper limit and a lower limit,

said thermostat being electrically connected to said heating element tocontrol the supply of electricity to said heating element, saidthermostat being positioned so that it is in thermal contact with thecontents of said reservoir and is responsive to the temperature of saidcoolant in said reservoir in both its liquid and vapor states, thesupply of electricity to said heating element being interrupted when thetemperature sensed by the thermostat reaches said upper limit, and beingresumed when said temperature falls .to said lower limit, said upperlimit being such that at least a portion of the liquid coolant in saidreservoir is vaporized when said heating element is energized and heatedcoolant is expelled through said outlet. the heating element beingdisconnected from its supply of electricity by said thermostat when saidupper limit has been reached whereupon the temperature in said reservoirfalls so that the vapor pressure in said reservoir drops substantiallythereby drawing a fresh charge of liquid coolant into said reservoirthrough said fluid inlet.

7. Apparatus as claimed in claim 6 wherein said fluid inlet and saidfluid outlet are substantially in alignment.

1. A heater for warming liquid coolant in a cooling system of an engineand for forcing said coolant through the cooling system without creatingany appreciable convection current in said heater, said heatercomprisIng: a. an enclosed reservoir for containing liquid coolant, saidreservoir having a fluid inlet and a fluid outlet to permit saidreservoir to be connected in said cooling system with said coolantsubstantially filling said reservoir; b. a one-way inlet valve incommunication with said fluid inlet to permit coolant to flow into saidreservoir and to prevent coolant from leaving said reservoir throughsaid fluid inlet; c. a one-way outlet valve in communication with saidfluid outlet to permit heated coolant to leave said reservoir and toprevent coolant from entering said reservoir through said fluid outlet;d. an electrical heating element coupled to said reservoir for heatingsaid coolant; and e. a thermostat having an upper limit and a lowerlimit, said thermostat being electrically connected to said heatingelement to control the supply of electricity to said heating element,said thermostat being positioned so that it is in thermal contact withthe contents of said reservoir and is responsive to the temperature ofsaid coolant in said reservoir in both its liquid and vapor states, thesupply of electricity to said heating element being interrupted when thetemperature sensed by the thermostat reaches said upper limit, and beingresumed when said temperature falls to said lower limit, said upperlimit being such that at least a portion of the liquid coolant in saidreservoir is vaporized when said heating element is energized and heatedcoolant is expelled through said outlet, the heating element beingdisconnected from its supply of electricity by said thermostat when saidupper limit has been reached, whereupon the temperature in saidreservoir falls so that the vapor pressure in said reservoir dropssubstantially thereby drawing a fresh charge of liquid coolant into saidreservoir through said fluid inlet.
 2. A heater as claimed in claim 1wherein said fluid inlet and said fluid outlet are substantially inalignment and said heating element is in said reservoir.
 3. A heater asclaimed in claim 2 wherein said inlet valve comprises a first disclikemember positioned at the inner end of said fluid inlet against an endwall of said reservoir, said first disclike member being pivotallymounted and the inner end of said fluid inlet being shaped to provide aseat for said first disclike member when said first disclike member ispressed against said fluid inlet inner end.
 4. A heater as claimed inclaim 3 wherein said outlet valve comprises a second disclike memberpositioned at the inner end of said fluid outlet against an opposite endwall of said reservoir, said second disclike member being pivotallymounted, and a washer secured to said opposite end wall and positionedinwardly of said second disclike member to provide a seat for the same.5. A heater as claimed in claim 2 wherein a portion of said heatingelement is adjacent to an inner surface of a wall of said reservoir, andsaid thermostat is in contact with an outer surface of said wallopposite said portion of said heating element, said wall being thermallyconductive.
 6. In combination with an engine cooling system containingliquid coolant, a heater for warming the liquid coolant and for forcingsaid coolant through the cooling system, the heater being positioned atabout the upper level of coolant in the system so that the heater issubstantially full of coolant; the heater comprising an enclosedreservoir for containing liquid coolant, said reservoir having a fluidinlet and a fluid outlet to permit said reservoir to be connected insaid cooling system with said coolant substantially filling saidreservoir; a one-way inlet valve in communication with said fluid inletto permit coolant to flow into said reservoir and to prevent coolantfrom leaving said reservoir through said fluid inlet; a one-way outletvalve in communication with said fluid outlet to permit heated coolantto leave said reservoir and to prevent coolant from entering saidreservoir through said fluid outlEt; an electrical heating elementcoupled to said reservoir for heating said coolant; and a thermostathaving an upper limit and a lower limit, said thermostat beingelectrically connected to said heating element to control the supply ofelectricity to said heating element, said thermostat being positioned sothat it is in thermal contact with the contents of said reservoir and isresponsive to the temperature of said coolant in said reservoir in bothits liquid and vapor states, the supply of electricity to said heatingelement being interrupted when the temperature sensed by the thermostatreaches said upper limit, and being resumed when said temperature fallsto said lower limit, said upper limit being such that at least a portionof the liquid coolant in said reservoir is vaporized when said heatingelement is energized and heated coolant is expelled through said outlet,the heating element being disconnected from its supply of electricity bysaid thermostat when said upper limit has been reached whereupon thetemperature in said reservoir falls so that the vapor pressure in saidreservoir drops substantially thereby drawing a fresh charge of liquidcoolant into said reservoir through said fluid inlet.
 7. Apparatus asclaimed in claim 6 wherein said fluid inlet and said fluid outlet aresubstantially in alignment.